Abstract

A comparative approach to the study of immune system development has been extremely useful in our understanding of this complex process. For example, it was first experimentally demonstrated in chickens that the immune system had two antigen specific components, T and B cells. This dichotomy was subsequently found to exist in organisms as diverse as humans and frogs.1,2 Extrapolation of many findings in mammalian B cell differentiation can often be readily made between humans and mice. However, we will discuss several instances where models of B cell development that have been derived from murine systems do not appear to be directly applicable to humans. In some cases the apparent differences may simply be due to the experimental systems employed, but in others there may be fundamental differences between the two species. Since our purpose is not to minimize the value of comparative analysis, recent data concerning early B cell development in humans that most likely is true in mice will also be discussed.